Towards a regional coupled ice sheet - ocean model for Antarctica

• Main Authors: Timmermann, Ralph, Goeller, Sebastian
• Format: Conference Object
• Language: unknown
• Published: 2016
• Subjects: Antarctic; Ronne Ice Shelf; Southern Ocean; The Antarctic; Antarc*; Antarctica; Filchner Ronne Ice Shelf; Filchner-Ronne Ice Shelf; Ice Sheet; Ice Shelf; Sea ice
• Online Access: https://epic.awi.de/id/eprint/41027/; https://epic.awi.de/id/eprint/41027/1/Timmermann2.pdf; https://hdl.handle.net/10013/epic.48007; https://hdl.handle.net/10013/epic.48007.d001

To study the interaction between the world ocean and the Antarctic ice sheet, a Regional Antarctic and Global Ocean (RAnGO) model has been developed. The coupled model is based on a global implementation of the Finite Element Sea ice Ocean Model (FESOM) with a mesh that is substantially refined in the Southern Ocean, particularly in its marginal seas and in the sub-ice shelf cavities. The Antarctic cryosphere is represented by a regional setup of the ice flow model RIMBAY. As a first step, the RIMBAY domain comprises the Filchner-Ronne Ice Shelf and the grounded ice in its catchment area up to the ice divides. At the base of the RIMBAY ice shelf, melt rates from FESOM’s ice shelf component are prescribed. RIMBAY returns ice thickness and the position of the grounding line. To adjust the FESOM domain to varying cavity geometries, we use a pre-computed mesh that comprises the present-day ocean plus areas that may potentially become ungrounded. For each coupling step, i.e. once per year, the coupler determines the area covered by ocean and removes grid nodes that are covered by grounded ice. Changes in water column thickness are easily handled by the terrain-following vertical coordinate system in the sub-ice cavity. Model runs with a 20th century climate forcing yield a quasi-stable grounding line position close to the presently observed state with only small fluctuations. In a centennial-scale warm-water-inflow scenario, the model suggests a gradual retreat of the grounding line mainly at Institute, Foundation and Support Force Ice Streams. A more dramatic response is prevented by the steep topography under most of the currently grounded ice.